Timber in architecture: tradition and modern applications

Timber is perhaps the oldest building material of all, yet in recent years it has been enjoying a genuine renaissance. Architects around the world are designing schools, offices and even residential towers in wood, while in interiors it remains synonymous with warmth and comfort.

Bulgaria has a long timber tradition – from National Revival houses, with their timber upper floors and covered verandas known as chardaks, to mountain chalets. Here we look at why the material is so relevant today, what its strengths and weaknesses are, and where it finds its most interesting applications.

Why is timber returning to modern architecture?

Timber is making a comeback because it combines a renewable origin with new technologies that allow it to compete with concrete and steel across many building types.

Trees absorb carbon dioxide as they grow, and part of that carbon stays locked in the wood for the entire life of the building. When the material comes from responsibly managed forests, it is one of the most sustainable choices in construction. It is also light, easy to work, and allows much of a building to be manufactured in a factory and assembled quickly on site.

What can we learn from the Bulgarian Revival house?

The National Revival house – the traditional townhouse of the 18th and 19th centuries – shows that timber lasts for centuries when it is placed in the right position and protected from moisture. Builders of that era had no chemical preservatives, but they had excellent detailing.

• A stone ground floor – the timber starts well above ground level, away from soil moisture and rain splash.
• Wide eaves – the roof shields the façade and the timber elements from direct rain.
• A light upper structure – timber-framed walls with solid or light infill keep the upper floor light and allow bay windows to project over the street.
• Verandas and timber ceilings – semi-open spaces for summer and carved ceilings, such as those in the houses of Plovdiv and Koprivshtitsa, which still impress with their craftsmanship today.

The same principles – raising the structure off the ground, generous eaves, ventilation – underpin contemporary timber buildings too; today they are simply complemented by calculations, insulation and engineered products.

What are the advantages and disadvantages of timber?

Timber has many advantages, but it needs careful design so that its weaknesses do not come to the fore.

Advantages

• A renewable resource with carbon stored in the structure.
• Lightness – less weight means lighter foundations and easier transport.
• Good thermal insulation compared with concrete and steel.
• Fast construction through prefabrication.
• Warmth and comfort – its natural texture and scent create a pleasant environment.

Disadvantages and how to address them

• Sensitivity to moisture – solved with correct detailing: roof overhangs, a plinth, ventilated façades and keeping the timber clear of the ground.
• Combustibility – in a fire, solid timber elements form a charred layer that protects the core; the design provides for suitable cross-sections, linings and fire protection.
• Insects and fungi – prevented with dry timber, protective treatment and good ventilation.
• Dimensional movement – timber swells and shrinks as humidity changes, which is accounted for in the details and joints.
• Maintenance – façades need periodic care, or a conscious decision to accept natural greying.

What are CLT and glued laminated timber?

These are engineered timber products that have made modern timber construction possible, with long spans and many storeys.

• Glued laminated timber (glulam) – thin boards glued together in one direction to form long, strong beams and columns. It is used for long-span roofs, halls and exposed structures.
• Cross-laminated timber (CLT) – layers of boards glued crosswise to form solid panels for walls and floor slabs. They behave much like reinforced concrete slabs but are far lighter.

Two well-known examples show their potential. Brock Commons Tallwood House at the University of British Columbia in Vancouver is an 18-storey student residence with a timber structure built around a concrete core. Mjøstårnet in the Norwegian town of Brumunddal is an 18-storey building with apartments, a hotel and offices, constructed with glulam – on completion it was the tallest timber building in the world.

Where is timber used today?

Today timber appears at every scale – from a piece of furniture to a multi-storey building.

Detached houses

Timber houses are most often built either as timber-frame structures (a frame of studs and beams with insulation between them) or from solid panels. They are popular for holiday homes and second homes, and increasingly for main residences too. A well-designed timber house can achieve very good energy efficiency.

Roofs and exposed structures

A timber roof is traditional for the Bulgarian house, and exposed beams in attic rooms and halls add a character that is hard to achieve with any other material.

Façades

Timber cladding – from treated pine and larch to thermally modified wood – gives a natural appearance and combines well with render, stone and glass. A ventilated façade prevents the timber from retaining moisture.

Interiors

Floors, wall panelling, ceilings, staircases and bespoke furniture. Timber is the easiest way to bring warmth into a minimalist interior.

Renovating old buildings

Timber is a natural choice when refurbishing old houses with timber floor structures and roofs – the new elements are compatible with the old ones and place no additional load on the walls.

How do you choose timber for your project?

The choice depends on where the timber sits in the building, the loads it carries and the moisture it will be exposed to.

1. Define the function. Structure, façade, flooring and furniture all have different requirements.
2. Assess the conditions. Outdoors and in wet rooms you need more durable species or modified timber.
3. Check the moisture content. Structural timber must be properly dried, otherwise it will distort after installation.
4. Look for certification of origin, such as FSC or PEFC, if sustainability matters to you.
5. Plan the maintenance. Decide in advance whether the façade will be refreshed with stains or left to grey naturally.
6. Work with a structural engineer. Timber structures are designed to the same rigorous standards as reinforced concrete ones.

Our approach at DARCH Projects

We love working with timber, both in the architectural design of houses and holiday homes and in interiors. We help you choose the species and the details that will protect it, and show you how it will look in photorealistic visualisations before construction even begins.

Frequently asked questions

Is a timber house better than a brick one?

Neither is better in principle – it depends on the design and the quality of construction. A timber house is quicker to build, lighter and can be highly energy efficient. A brick house has greater thermal mass and is more familiar to most builders in Bulgaria. What really matters is the quality of the detailing, the insulation and the protection from moisture.

What is CLT?

CLT (cross-laminated timber) is an engineered wood product in which layers of boards are glued crosswise at right angles. The result is large, stable and relatively light panels for walls, floors and roofs. They are manufactured with great precision in a factory and allow multi-storey timber buildings to be erected quickly.

Do timber buildings burn easily?

Solid timber elements burn more predictably than most people expect. In a fire, a charred layer forms on the surface, slowing the burning of the core and helping the structure to hold. Fire safety is achieved through correct sizing, protective linings, fire-retardant products and a design that complies with the relevant regulations.

How long does a timber façade last?

Durability depends on the species, the treatment and, above all, the detailing. A façade that is ventilated, sheltered by eaves and raised above the ground can last for many years. Without maintenance, timber greys naturally; if you want to keep its colour, a stain is applied at the intervals recommended by the manufacturer.